Optical imaging system

ABSTRACT

There is provided an optical imaging system including a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens. The first lens includes a negative refractive power and a concave object-side surface. The second lens includes a concave object-side surface. The fourth lens includes a negative refractive power. The sixth lens includes an inflection point formed on an image-side surface thereof. The first to sixth lenses are sequentially disposed from an object side toward an imaging plane.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/502,485 filed on Jul. 3, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/887,253 filed on Feb. 2, 2018, now U.S. Pat. No.10,386,612, which is a divisional of U.S. patent application Ser. No.15/187,918 filed on Jun. 21, 2016, now U.S. Pat. No. 9,952,409, whichclaims the benefit under 35 USC § 119(a) of Korean Patent ApplicationNo. 10-2015-0145260 filed on Oct. 19, 2015, in the Korean IntellectualProperty Office, the entire disclosures of each of which areincorporated herein by reference for all purposes.

BACKGROUND 1. Field

The following description relates to an optical imaging system includinglenses.

2. Description of Related Art

A plurality of optical imaging systems may be mounted in a portableterminal. For example, optical imaging systems may be mounted on each ofa front surface and a rear surface of the portable terminal.

The optical imaging system mounted on the rear surface of the portableterminal may be used to image a subject located at a relatively longdistance. On the other hand, the optical imaging system mounted on thefront surface of the portable terminal is used to image a subjectlocated at a relatively short distance. However, the optical imagingsystem mounted on the front surface of the portable terminal maygenerate an optical distortion phenomenon, such as “cone-head.”Therefore, there is a need to develop an optical imaging system capableof reducing optical distortions, such as “cone-head” distortions, andbeing appropriate for imaging a subject at a relatively short distance.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

In accordance with an embodiment, there is provided an optical imagingsystem, including: a first lens including a negative refractive powerand a concave object-side surface; a second lens including a concaveobject-side surface; a third lens; a fourth lens including a negativerefractive power; a fifth lens; and a sixth lens including an inflectionpoint formed on an image-side surface thereof, wherein the first tosixth lenses are sequentially disposed from an object side toward animaging plane.

The second lens may include a positive refractive power.

The third lens may include a positive refractive power.

The fifth lens may include a positive refractive power.

The sixth lens may include a negative refractive power.

−35.0<{(1/f)*(Y/tan θ)−1}*100<−5.0, in which f may be an overall focallength of the optical imaging system, Y may be ½ of a diagonal length ofthe imaging plane, and θ may be equal to half a field of view of theoptical imaging system.

TL/2Y<0.95, in which TL may be a distance from the object-side surfaceof the first lens to the imaging plane, and 2Y may be a diagonal lengthof the imaging plane.

R1/f<−0.5, in which f may be an overall focal length of the opticalimaging system, and R1 may be a radius of curvature of the object-sidesurface of the first lens.

−5.5<(R1+R2)/(R1−R2)<0.5, in which R1 may be a radius of curvature ofthe object-side surface of the first lens, and R2 may be a radius ofcurvature of an image-side surface of the first lens.

−1.5<f/f1<−0.05, in which f may be an overall focal length of theoptical imaging system, and f1 may be a focal length of the first lens.

0.5<f/f3<2.0, in which f may be an overall focal length of the opticalimaging system, and f3 may be a focal length of the third lens.

0.7<|f/f6|<1.8, in which f may be an overall focal length of the opticalimaging system, and f6 may be a focal length of the sixth lens.

1.5<f/EPD<2.1, in which f may be an overall focal length of the opticalimaging system, and EPD may be an entrance pupil diameter of the opticalimaging system.

0.4<(t1+t2)/t3<1.3, in which t1 may be a thickness at an optical axiscenter of the first lens, t2 may be a thickness at an optical axiscenter of the second lens, and t3 may be a thickness at an optical axiscenter of the third lens.

0<|n1−n2|<0.25, in which n1 may be a refractive index of the first lens,and n2 may be a refractive index of the second lens.

In accordance with an embodiment, there is provided an optical imagingsystem, including: a first lens including a concave object-side surface;a second lens including a convex image-side surface; a third lens havingincluding a convex object-side surface and a convex image-side surface;a fourth lens; a fifth lens; and a sixth lens including an inflectionpoint formed on an image-side surface thereof, wherein the first tosixth lenses are sequentially disposed from an object side toward animaging plane.

In accordance with another embodiment, there is provided an opticalimaging system, including: a first lens including a concave image-sidesurface and a concave image-side surface; a second lens including aconcave image-side surface and a convex image-side surface; a third lensincluding a convex object-side surface and a convex image-side surface;a fourth lens; a fifth lens; and a sixth lens including a concaveimage-side surface, wherein the first, the fourth, and the sixth lenseshave a same refractive power, different than a refractive power of thethird and fourth lenses.

The first, the second, the fourth, and the sixth lenses may include anegative refractive power.

The second, the third, and the fourth lenses may include a positiverefractive power.

The fourth lens may include a meniscus shape and the fifth lens mayinclude a concave object-side surface and a convex image-side surface.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings in which:

FIG. 1 is a view of an optical imaging system, according to a firstembodiment;

FIG. 2 is graphs displaying aberration curves of the optical imagingsystem illustrated in FIG. 1 ;

FIG. 3 is a table displaying characteristics of lenses of the opticalimaging system illustrated in FIG. 1 ;

FIG. 4 is a table displaying aspherical characteristics of the opticalimaging system illustrated in FIG. 1 ;

FIG. 5 is a view of an optical imaging system, according to a secondembodiment;

FIG. 6 is graphs displaying aberration curves of the optical imagingsystem illustrated in FIG. 5 ;

FIG. 7 is a table displaying characteristics of lenses of the opticalimaging system illustrated in FIG. 5 ;

FIG. 8 is a table displaying aspherical characteristics of the opticalimaging system illustrated in FIG. 5 ;

FIG. 9 is a view of an optical imaging system, according to a thirdembodiment;

FIG. 10 is graphs displaying aberration curves of the optical imagingsystem illustrated in FIG. 9 ;

FIG. 11 is a table displaying characteristics of lenses of the opticalimaging system illustrated in FIG. 9 ;

FIG. 12 is a table displaying aspherical characteristics of the opticalimaging system illustrated in FIG. 9 ;

FIG. 13 is a view of an optical imaging system, according to a fourthembodiment;

FIG. 14 is graphs displaying aberration curves of the optical imagingsystem illustrated in FIG. 13 ;

FIG. 15 is a table displaying characteristics of lenses of the opticalimaging system illustrated in FIG. 13 ;

FIG. 16 is a table displaying aspherical characteristics of the opticalimaging system illustrated in FIG. 13 ;

FIG. 17 is a view of an optical imaging system, according to a fifthembodiment;

FIG. 18 is graphs displaying aberration curves of the optical imagingsystem illustrated in FIG. 17 ;

FIG. 19 is a table displaying characteristics of lenses of the opticalimaging system illustrated in FIG. 17 ;

FIG. 20 is a table displaying aspherical characteristics of the opticalimaging system illustrated in FIG. 17 ;

FIG. 21 is a view of an optical imaging system, according to a sixthembodiment;

FIG. 22 is graphs displaying aberration curves of the optical imagingsystem illustrated in FIG. 21 ;

FIG. 23 is a table displaying characteristics of lenses of the opticalimaging system illustrated in FIG. 21 ; and

FIG. 24 is a table displaying aspherical characteristics of the opticalimaging system illustrated in FIG. 21 .

Throughout the drawings and the detailed description, unless otherwisedescribed, the same drawing reference numerals will be understood torefer to the same elements, features, and structures. The relative sizeand depiction of these elements may be exaggerated for clarity,illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. However, various changes,modifications, and equivalents of the methods, apparatuses, and/orsystems described herein will be apparent to one of ordinary skill inthe art. The sequences of operations described herein are merelyexamples, and are not limited to those set forth herein, but may bechanged as will be apparent to one of ordinary skill in the art, withthe exception of operations necessarily occurring in a certain order.Also, descriptions of functions and constructions that are well known toone of ordinary skill in the art may be omitted for increased clarityand conciseness.

The features described herein may be embodied in different forms, andare not to be construed as being limited to the examples describedherein. Rather, the examples described herein have been provided so thatthis disclosure will be thorough and complete, and will convey the fullscope of the disclosure to one of ordinary skill in the art.

Throughout the specification, it will be understood that when anelement, such as a layer, region or wafer (substrate), is referred to asbeing “on,” “connected to,” or “coupled to” another element, it can bedirectly “on,” “connected to,” or “coupled to” the other element orother elements intervening therebetween may be present. In contrast,when an element is referred to as being “directly on,” “directlyconnected to,” or “directly coupled to” another element, there may be noelements or layers intervening therebetween. Like numerals refer to likeelements throughout. As used herein, the term “and/or” includes any andall combinations of one or more of the associated listed items.

It will be apparent that though the terms first, second, third, etc. maybe used herein to describe various members, components, regions, layersand/or sections, these members, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one member, component, region, layer or section fromanother region, layer or section. Thus, a first member, component,region, layer or section discussed below could be termed a secondmember, component, region, layer or section without departing from theteachings of the embodiments.

Spatially relative terms, such as “above,” “upper,” “below,” and “lower”and the like, may be used herein for ease of description to describe oneelement's relationship to another element(s) as shown in the figures. Itwill be understood that the spatially relative terms are intended toencompass different orientations of the device in use or operation inaddition to the orientation depicted in the figures. For example, if thedevice in the figures is turned over, elements described as “above,” or“upper” other elements would then be oriented “below,” or “lower” theother elements or features. Thus, the term “above” can encompass boththe above and below orientations depending on a particular direction ofthe figures. The device may be otherwise oriented (rotated 90 degrees orat other orientations) and the spatially relative descriptors usedherein may be interpreted accordingly.

The terminology used herein is for describing particular embodimentsonly and is not intended to be limiting. As used herein, the singularforms “a,” “an,” and “the” are intended to include the plural forms aswell, unless the context clearly indicates otherwise. It will be furtherunderstood that the terms “comprises,” and/or “comprising” when used inthis specification, specify the presence of stated features, integers,steps, operations, members, elements, and/or groups thereof, but do notpreclude the presence or addition of one or more other features,integers, steps, operations, members, elements, and/or groups thereof.

Hereinafter, various embodiments will be described with reference toschematic views illustrating embodiments. In the drawings, for example,due to manufacturing techniques and/or tolerances, modifications of theshape shown may be estimated. Thus, embodiments should not be construedas being limited to the particular shapes of regions shown herein, forexample, to include a change in shape results in manufacturing. Thefollowing embodiments may also be constituted by one or a combinationthereof.

The various embodiments described below may have a variety ofconfigurations and propose only a required configuration herein, but arenot limited thereto.

In addition, a surface of each lens closest to an object is referred toas a first surface or an object-side surface, and a surface of each lensclosest to an imaging surface is referred to as a second surface or animage-side surface. A person skilled in the relevant art will appreciatethat other units of measurement may be used. Further, in the presentspecification, all radii of curvature, thicknesses, OALs (optical axisdistances from the first surface of the first lens to the image sensor(OALs), a distance on the optical axis between the stop and the imagesensor (SLs), a through-the-lens (TTL), image heights or ½ of a diagonallength of the imaging plane (IMGHs) (image heights), and black focuslengths (BFLs) (back focus lengths) of the lenses, an overall focallength of an optical system, and a focal length of each lens areindicated in millimeters (mm). Further, thicknesses of lenses, gapsbetween the lenses, OALs, and SLs are distances measured based on anoptical axis of the lenses.

Further, in a description for shapes of the lenses, surface of a lensbeing convex means that an optical axis portion of a correspondingsurface is convex, and a surface of a lens being concave means that anoptical axis portion of a corresponding surface is concave. Therefore,even in the case that one surface of a lens is described as beingconvex, an edge portion of the lens may be concave. Likewise, even inthe case that one surface of a lens is described as being concave, anedge portion of the lens may be convex. In other words, a paraxialregion of a lens may be convex, while the remaining portion of the lensoutside the paraxial region is either convex, concave, or flat. Further,a paraxial region of a lens may be concave, while the remaining portionof the lens outside the paraxial region is either convex, concave, orflat.

In the optical system, according to embodiments, the first to fifthlenses are formed of materials including glass, plastic or other similartypes of polycarbonate materials. In another embodiment, at least one ofthe first through fifth lenses is formed of a material different fromthe materials forming the other first through fifth lenses.

An optical imaging system includes an optical system including lenses.For example, the optical system of the optical imaging system mayinclude five lenses having refractive power. However, the opticalimaging system is not limited to including only the lenses having therefractive power. For example, the optical imaging system may include astop to control an amount of light. In addition, the optical imagingsystem may further include an infrared cut-off filter filtering infraredlight. Further, the optical imaging system may further include an imagesensor, such as an imaging device, configured to convert an image of asubject incident thereto through the optical system into electricalsignals. Further, the optical imaging system may further include a gapmaintaining member adjusting a gap between lenses.

First to sixth lenses are formed of materials having a refractive indexdifferent from that of air. For example, the first to sixth lenses areformed of plastic or glass. At least one of the first to sixth lenseshas an aspherical shape. As one example, only the sixth lens of thefirst to sixth lenses may have the aspherical shape. In addition, atleast one surface of all of the first to sixth lenses is aspherical. Inan example, the aspherical surface of each lens may be represented bythe following Equation 1:

$\begin{matrix}{Z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {Ar}^{4} + {Br}^{6} + {Cr}^{8} + {Dr}^{10} + {Er}^{12} + {Fr}^{14} + {Gr}^{16} + {Hr}^{18} + {Jr}^{20}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In this equation, c is an inverse of a radius of curvature of the lens,k is a conic constant, r is a distance from a certain point on anaspherical surface of the lens to an optical axis, A to J are asphericalconstants, and Z (or SAG) is a distance between a certain point on theaspherical surface of the lens at the distance Y and a tangential planemeeting the apex of the aspherical surface of the lens.

In accordance with an embodiment, an optical imaging system includes sixlenses, a filter, an image sensor, and a stop. Next, the above-mentionedcomponents will be described.

The first lens has a refractive power. For example, the first lens has anegative refractive power.

At least one surface of the first lens is concave. For example, anobject-side surface of the first lens is concave. In one example, animage-side surface of the first lens is concave in a paraxial region andgradually outwardly curves (such as inflection points), at edge portionsthereof. An object-side surface of the first lens is concave in theparaxial region and gradually flattens at edge or end portions of thefirst lens.

The first lens has an aspherical surface. For example, both surfaces ofthe first lens are aspherical. The first lens is formed of a materialhaving high light transmissivity and excellent workability. For example,the first lens is formed of plastic. However, a material of the firstlens is not limited to plastic. For example, the first lens may beformed of glass.

The second lens has a refractive power. For example, the second lens hasa positive refractive power or a negative refractive power.

At least one surface of the second lens is convex. For example, animage-side surface of the second lens is convex. In this example, anobject-side surface of the second lens is concave in a paraxial region.In another embodiment, an image-side surface of the second lens isconcave and the object-side surface of the second lens is convex. In oneembodiment, end portions of the object-side surface of the second lensoverlaps, at least in part, with at least a portion of the first lens.In another embodiment, the second lens is spaced apart from the firstlens.

The second lens has an aspherical surface. For example, an object-sidesurface of the second lens is aspherical. The second lens is formed of amaterial having high light transmissivity and excellent workability. Forexample, the second lens is formed of plastic. However, a material ofthe second lens is not limited to the plastic. For example, the secondlens is formed of glass.

The third lens has a refractive power. For example, the third lens has apositive refractive power.

At least one surface of the third lens is convex. For example, bothsurfaces of the third lens is convex. In one example, an object-sidesurface of the third lens is convex in a paraxial region and graduallyflattens or substantially flattens at edge portions thereof. Animage-side surface of the second lens is convex, encompassing an entireimage-side surface thereof.

The third lens has an aspherical surface. For example, an image-sidesurface of the third lens is aspherical. The third lens is formed of amaterial having high light transmissivity and excellent workability. Forexample, the third lens is formed of plastic. However, a material of thethird lens is not limited to the plastic. For example, the third lensmay be formed of glass.

The fourth lens has a refractive power. For example, the fourth lens hasa negative refractive power.

The fourth lens has a meniscus shape. For example, an object-sidesurface of the fourth lens is convex and an image-side surface of thefourth lens is concave. In an alternative embodiment, the object-sidesurface of the fourth lens is convex in a paraxial region and theimage-side surface of the fourth lens is concave. In a furtherembodiment, the object-side surface of the fourth lens is flat orsubstantially flat in a paraxial region and the image-side surface ofthe fourth lens is concave. In one embodiment, the third lens and thefourth lens are spaced apart. In another embodiment, the third lens andthe fourth lens are in contact with each other.

The fourth lens has an aspherical surface. For example, both surfaces ofthe fourth lens is aspherical. The fourth lens is formed of a materialhaving high light transmissivity and excellent workability. For example,the fourth lens is formed of plastic. However, a material of the fourthlens is not limited to the plastic. For example, the fourth lens may beformed of glass.

The fifth lens has a refractive power. For example, the fifth lens has apositive refractive power.

At least one surface of the fifth lens is convex. For example, animage-side surface of the fifth lens is convex. In one example, anobject-side surface of the fifth lens is concave in a paraxial regionand gradually flattens or substantially flattens at portions thereof andoutwardly extends at an angle at end portions thereof. An image-sidesurface of the second lens is convex in a paraxial region and flattensor substantially flattens at end portions thereof. In another example,the object-side surface of the fifth lens is convex in a paraxial regionand gradually flattens or substantially flattens at portions thereof andoutwardly extends at an angle at end portions thereof, and theimage-side surface of the second lens is convex in a paraxial region andflattens or substantially flattens at end portions thereof.

The fifth lens has an aspherical surface. For example, both surfaces ofthe fifth lens are aspherical. The fifth lens is formed of a materialhaving high light transmissivity and excellent workability. For example,the fifth lens is formed of plastic. However, a material of the fifthlens is not limited to the plastic. For example, the fifth lens isformed of glass.

The sixth lens has a refractive power. For example, the sixth lens has anegative refractive power.

The sixth lens has a meniscus shape. For example, an image-side surfaceof the sixth lens is concave. In an example, an object-side surface ofthe sixth lens is concave in a paraxial region.

The sixth lens has inflection points. For example, the inflection pointsmay be formed on both surfaces of the sixth lens.

The sixth lens has an aspherical surface. For example, both surfaces ofthe sixth lens are aspherical. The sixth lens is formed of a materialhaving high light transmissivity and excellent workability. For example,the sixth lens is formed of plastic. However, a material of the sixthlens is not limited to the plastic. For example, the sixth lens may beformed of glass.

A person of ordinary skill in the relevant art will appreciate that eachof the first through sixth lenses may be configured in an oppositerefractive power from the configuration described above. For example, inan alternative configuration, the first lens has a positive refractivepower, the second lens has a positive refractive power, the third lenshas a negative refractive power, the fourth lens has a positiverefractive power, the fifth lens has a negative refractive power, andthe sixth lens has a positive refractive power. Other variations of therefractive power for the above-described embodiment may be implemented.

The filter filters certain wavelengths of light from incident lightincident through the first to sixth lenses. For example, the filterfilters infrared wavelengths of the incident light.

The filter is manufactured to have a relatively thin thickness. To thisend, the filter is formed of plastic.

The image sensor is configured to realize a high degree of resolution.For example, a unit size of the pixels configuring the image sensor maybe 1.12 μm or less.

The stop is disposed in order to adjust an amount of light incident tothe lenses. For example, the stop is disposed or adjacently disposedbetween the second and third lenses. However, a person skilled in theart will appreciate that the stop may be placed at other positions, suchas in front of the first lens, and more than one stop may beimplemented.

The optical imaging system satisfies the following ConditionalExpressions 1 through 11:−35.0<{(1/f)*(Y/tan θ)−1}*100<−5.0  [Conditional Expression 1]TL/2Y<0.95  [Conditional Expression 2]R1/f<−0.5  [Conditional Expression 3]−5.5<(R1+R2)/(R1−R2)<0.5  [Conditional Expression 4]−1.5<f/f1<−0.05  [Conditional Expression 5]0.5<f/f3<2.0  [Conditional Expression 6]0.7<|f/f6|<1.8  [Conditional Expression 7]0.9<tan θ  [Conditional Expression 8]1.5<f/EPD<2.1  [Conditional Expression 9]0.4<(t1+t2)/t3<1.3  [Conditional Expression 10]0<|n1−n2|<0.25.  [Conditional Expression 11]

In an example, f is an overall focal length of the optical imagingsystem, 2Y is a diagonal length of an imaging plane, Y is ½ of 2Y, θ isequal to half a field of view of the optical imaging system, R1 is aradius of curvature of the object-side surface of the first lens, R2 isa radius of curvature of an image-side surface of the first lens, f1 isa focal length of the first lens, f3 is a focal length of the thirdlens, f6 is a focal length of the sixth lens, EPD is an entrance pupildiameter (EPD), t1 is a thickness at an optical axis center of the firstlens, t2 is a thickness at an optical axis center of the second lens, t3is a thickness at an optical axis center of the third lens, n1 is arefractive index of the first lens, and n2 is a refractive index of thesecond lens.

The optical imaging system satisfying the above Conditional Expressions1 through 11 may be miniaturized, and may allow high resolution imagesto be realized.

Next, optical imaging systems, according to several embodiments, will bedescribed.

An optical imaging system, according to a first embodiment, will bedescribed with reference to FIG. 1 .

The optical imaging system 100, according to the first embodiment,includes an optical system including a first lens 110, a second lens120, a third lens 130, a fourth lens 140, a fifth lens 150, and a sixthlens 160.

The optical imaging system 100 includes a filter 170, an image sensor180, and a stop ST. The filter 170 is disposed between the sixth lens160 and the image sensor 180, and the stop ST is disposed between thesecond lens 120 and the third lens 130.

In an embodiment, the first lens 110 has a negative refractive power,and an object-side surface thereof is concave and an image-side surfacethereof may be convex. The second lens 120 has a positive refractivepower, and an object-side surface thereof is concave and an image-sidesurface thereof is convex. The third lens 130 has a positive refractivepower, and an object-side surface and an image-side surface thereof areconvex. The fourth lens 140 has a negative refractive power, and anobject-side surface thereof is convex and an image-side surface thereofis concave. The fifth lens 150 has a positive refractive power, and anobject-side surface thereof is convex and an image-side surface thereofis convex. The sixth lens 160 has a negative refractive power, and anobject-side surface thereof is convex and an image-side surface thereofis concave. In addition, inflection points are formed on both surfacesof the sixth lens 160.

The optical imaging system configured as described above may representaberration characteristics as illustrated in FIG. 2 . FIGS. 3 and 4 aretables displaying characteristics of lenses and asphericalcharacteristics of the optical imaging system, according to the firstembodiment.

An optical imaging system, according to a second embodiment, will bedescribed with reference to FIG. 5 .

The optical imaging system 200, according to the second embodiment,includes an optical system including a first lens 210, a second lens220, a third lens 230, a fourth lens 240, a fifth lens 250, and a sixthlens 260.

The optical imaging system 200 includes a filter 270, an image sensor280, and a stop ST. The filter 270 is disposed between the sixth lens260 and the image sensor 280, and the stop ST is disposed between thesecond lens 220 and the third lens 230.

In an embodiment, the first lens 210 has a negative refractive power,and an object-side surface thereof is concave and an image-side surfacethereof may be convex. The second lens 220 has a negative refractivepower, and an object-side surface thereof is concave and an image-sidesurface thereof is convex. The third lens 230 has a positive refractivepower, and an object-side surface and an image-side surface thereof areconvex. The fourth lens 240 has a negative refractive power, and anobject-side surface thereof is convex and an image-side surface thereofis concave. The fifth lens 250 has a positive refractive power, and anobject-side surface thereof is concave and an image-side surface thereofis convex. The sixth lens 260 has a negative refractive power, and anobject-side surface thereof is convex and an image-side surface thereofis concave. In addition, inflection points are formed on both surfacesof the sixth lens 260.

The optical imaging system configured as described above may representaberration characteristics as illustrated in FIG. 6 . FIGS. 7 and 8 aretables displaying characteristics of lenses and asphericalcharacteristics of the optical imaging system, according to the secondembodiment.

An optical imaging system, according to a third embodiment, will bedescribed with reference to FIG. 9 .

The optical imaging system 300, according to the third embodiment,includes an optical system including a first lens 310, a second lens320, a third lens 330, a fourth lens 340, a fifth lens 350, and a sixthlens 360.

The optical imaging system 300 includes a filter 370, an image sensor380, and a stop ST. The filter 370 is disposed between the sixth lens360 and the image sensor 380, and the stop ST is disposed between thesecond lens 320 and the third lens 330.

In an embodiment, the first lens 310 has a negative refractive power,and an object-side surface thereof is concave and an image-side surfacethereof may be convex. The second lens 320 has a negative refractivepower, and an object-side surface thereof is concave and an image-sidesurface thereof is convex. The third lens 330 has a positive refractivepower, and an object-side surface and an image-side surface thereof areconvex. The fourth lens 340 has a negative refractive power, and anobject-side surface thereof is convex and an image-side surface thereofis concave. The fifth lens 350 has a positive refractive power, and anobject-side surface thereof is concave and an image-side surface thereofis convex. The sixth lens 360 has a negative refractive power, and anobject-side surface thereof is convex and an image-side surface thereofis concave. In addition, inflection points are formed on both surfacesof the sixth lens 360.

The optical imaging system configured as described above may representaberration characteristics as illustrated in FIG. 10 . FIGS. 11 and 12are tables displaying characteristics of lenses and asphericalcharacteristics of the optical imaging system, according to the thirdembodiment.

An optical imaging system, according to a fourth embodiment, will bedescribed with reference to FIG. 13 .

The optical imaging system 400, according to the fourth embodiment,includes an optical system including a first lens 410, a second lens420, a third lens 430, a fourth lens 440, a fifth lens 450, and a sixthlens 460.

The optical imaging system 400 includes a filter 470, an image sensor480, and a stop ST. The filter 470 is disposed between the sixth lens460 and the image sensor 480, and the stop ST is disposed between thesecond lens 420 and the third lens 430.

In an embodiment, the first lens 410 has a negative refractive power,and an object-side surface thereof is concave and an image-side surfacethereof is convex. The second lens 420 has a negative refractive power,and an object-side surface thereof is concave and an image-side surfacethereof is convex. The image-side surface of the first lens 410 and theobject-side surface of the second lens 420, in one embodiment, touch oroverlap at a point or portions thereof. The third lens 430 has apositive refractive power, and an object-side surface and an image-sidesurface thereof are convex. The fourth lens 440 has a negativerefractive power, and an object-side surface thereof is convex and animage-side surface thereof is concave. The fifth lens 450 has a positiverefractive power, and an object-side surface thereof is convex and animage-side surface thereof is convex. The sixth lens 460 has a negativerefractive power, and an object-side surface thereof is convex and animage-side surface thereof is concave. In addition, inflection pointsare formed on both surfaces of the sixth lens 460.

The optical imaging system configured as described above may representaberration characteristics as illustrated in FIG. 14 . FIGS. 15 and 16are tables displaying characteristics of lenses and asphericalcharacteristics of the optical imaging system, according to the fourthembodiment.

An optical imaging system, according to a fifth embodiment, will bedescribed with reference to FIG. 17 .

The optical imaging system 500, according to the fifth embodiment,includes an optical system including a first lens 510, a second lens520, a third lens 530, a fourth lens 540, a fifth lens 550, and a sixthlens 560.

The optical imaging system 500 includes a filter 570, an image sensor580, and a stop ST. The filter 570 is disposed between the sixth lens560 and the image sensor 580, and the stop ST is disposed between thesecond lens 520 and the third lens 530.

In an embodiment, the first lens 510 has a negative refractive power,and an object-side surface thereof is concave and an image-side surfacethereof is convex. The second lens 520 has a negative refractive power,and an object-side surface thereof is concave and an image-side surfacethereof is convex. The third lens 530 has a positive refractive power,and an object-side surface and an image-side surface thereof are convex.The fourth lens 540 has a negative refractive power, and an object-sidesurface thereof is convex and an image-side surface thereof is concave.The fifth lens 550 has a positive refractive power, and an object-sidesurface thereof is concave and an image-side surface thereof is convex.The sixth lens 560 has a negative refractive power, and an object-sidesurface thereof is convex and an image-side surface thereof is concave.In addition, inflection points are formed on both surfaces of the sixthlens 560.

The optical imaging system configured as described above may representaberration characteristics as illustrated in FIG. 18 . FIGS. 19 and 20are tables displaying characteristics of lenses and asphericalcharacteristics of the optical imaging system, according to the fifthembodiment.

An optical imaging system, according to a sixth embodiment, will bedescribed with reference to FIG. 21 .

The optical imaging system 600, according to the sixth embodiment,includes an optical system including a first lens 610, a second lens620, a third lens 630, a fourth lens 640, a fifth lens 650, and a sixthlens 660.

The optical imaging system 600 includes a filter 670, an image sensor680, and a stop ST. The filter 670 is disposed between the sixth lens660 and the image sensor 680, and the stop ST is disposed between thesecond lens 620 and the third lens 630.

In an embodiment, the first lens 610 has a negative refractive power,and an object-side surface thereof is concave and an image-side surfacethereof is concave. The second lens 620 may have positive refractivepower, and an object-side surface and an image-side surface thereof areconvex. The third lens 630 has a positive refractive power, and anobject-side surface and an image-side surface thereof are convex. Thefourth lens 640 has a negative refractive power, and an object-sidesurface thereof is convex and an image-side surface thereof is concave.The fifth lens 650 has a positive refractive power, and an object-sidesurface thereof is concave and an image-side surface thereof is convex.The sixth lens 660 has a negative refractive power, and an object-sidesurface thereof is concave and an image-side surface thereof is concave.In addition, inflection points are formed on both surfaces of the sixthlens 660.

The optical imaging system, configured as described above, may representaberration characteristics as illustrated in FIG. 22 . FIGS. 23 and 24are tables displaying characteristics of lenses and asphericalcharacteristics of the optical imaging system, according to the sixthembodiment.

Table 1 represents values of Conditional Expressions 1 through 11 of theoptical imaging systems, according to the first to sixth embodiments.

TABLE 1 First Second Third Fourth Fifth Sixth Em- Em- Em- Em- Em- Em-Conditional bodi- bodi- bodi- bodi- bodi- bodi- Expression ment mentment ment ment ment {(1/f) * −24.00 −16.15 −20.04 −19.99 −24.00 −9.11(Y/tanθ) − 1} * 100 TL/2Y 0.900 0.910 0.900 0.900 0.890 0.950 R1/f−1.360 −1.360 −1.440 −1.330 −1.250 −1.170 (R1 + R2)/ −3.430 −3.870−3.350 −3.880 −4.510 0.040 (R1 − R2) f/f1 −0.170 −0.160 −0.170 −0.160−0.150 −0.990 f/f3 1.330 1.340 1.330 1.330 1.410 1.200 |f/f6| 1.1401.150 1.100 1.170 1.180 1.250 tanθ 1.299 1.175 1.322 1.271 1.087 1.099f/EPD 1.850 1.870 1.850 1.850 1.830 1.900 (t1 + t2)/t3 0.721 0.714 0.6480.719 0.582 1.038 |n1 − n2| 0.099 0.107 0.107 0.099 0.099 0.045

As set forth above, according to various embodiments, the opticalimaging system that reduces a wide angle distortion phenomenon may berealized.

While this disclosure includes specific examples, it will be apparent toone of ordinary skill in the art that various changes in form anddetails may be made in these examples without departing from the spiritand scope of the claims and their equivalents. The examples describedherein are to be considered in a descriptive sense only, and not forpurposes of limitation. Descriptions of features or aspects in eachexample are to be considered as being applicable to similar features oraspects in other examples. Suitable results may be achieved if thedescribed techniques are performed in a different order, and/or ifcomponents in a described system, architecture, device, or circuit arecombined in a different manner and/or replaced or supplemented by othercomponents or their equivalents. Therefore, the scope of the disclosureis defined not by the detailed description, but by the claims and theirequivalents, and all variations within the scope of the claims and theirequivalents are to be construed as being included in the disclosure.

What is claimed is:
 1. An optical imaging system, comprising: a firstlens comprising a negative refractive power; a second lens comprising apositive refractive power; a third lens; a fourth lens comprising anegative refractive power and a convex object-side surface; a fifthlens; and a sixth lens comprising an inflection point formed on animage-side surface thereof, wherein the first to sixth lenses aresequentially disposed from an object side toward an imaging plane, andwherein an absolute value of a radius of curvature of an image-sidesurface of the first lens is greater than an absolute value of a radiuscurvature of an object-side surface of the second lens.
 2. The opticalimaging system of claim 1, wherein the third lens comprises a positiverefractive power.
 3. The optical imaging system of claim 1, wherein thefifth lens comprises a positive refractive power.
 4. The optical imagingsystem of claim 1, wherein the sixth lens comprises a negativerefractive power.
 5. The optical imaging system of claim 1, wherein−35.0<{(1/f)*(Y/tan θ)−1}*100<−5.0, in which f is an overall focallength of the optical imaging system, Y is ½ of a diagonal length of theimaging plane, and θ is equal to half a field of view of the opticalimaging system.
 6. The optical imaging system of claim 1, whereinTL/2Y<0.95, in which TL is a distance from the object-side surface ofthe first lens to the imaging plane, and 2Y is a diagonal length of theimaging plane.
 7. The optical imaging system of claim 1, wherein−5.5<(R1+R2)/(R1−R2)<0.5, in which R1 is a radius of curvature of theobject-side surface of the first lens, and R2 is a radius of curvatureof an image-side surface of the first lens.
 8. The optical imagingsystem of claim 1, wherein −1.5<f/f1<−0.05, in which f is an overallfocal length of the optical imaging system, and f1 is a focal length ofthe first lens.
 9. The optical imaging system of claim 1, wherein1.5<f/EPD<2.1, in which f is an overall focal length of the opticalimaging system, and EPD is an entrance pupil diameter of the opticalimaging system.
 10. The optical imaging system of claim 1, wherein0<|n1−n2|<0.25, in which n1 is a refractive index of the first lens, andn2 is a refractive index of the second lens.
 11. An optical imagingsystem, comprising: a first lens comprising a negative refractive powerand a concave object-side surface; a second lens comprising a positiverefractive power and a convex object-side surface; a third lens; afourth lens comprising a negative refractive power; a fifth lenscomprising a convex image-side surface; and a sixth lens comprising aconcave image-side surface and an inflection point formed on animage-side surface thereof, wherein the first to sixth lenses aresequentially disposed from an object side toward an imaging plane, andwherein a value of a radius curvature of an object-side surface of thethird lens is greater than a value of a radius curvature of animage-side surface of the third lens.
 12. The optical imaging system ofclaim 11, wherein R1/f<−0.5, in which f is an overall focal length ofthe optical imaging system, and R1 is a radius of curvature of theobject-side surface of the first lens.
 13. The optical imaging system ofclaim 11, wherein 0.5<f/f3<2.0, in which f is an overall focal length ofthe optical imaging system, and f3 is a focal length of the third lens.14. The optical imaging system of claim 11, wherein 0.4<(t1+t2)/t3<1.3,in which t1 is a thickness at an optical axis center of the first lens,t2 is a thickness at an optical axis center of the second lens, and t3is a thickness at an optical axis center of the third lens.